Spending 25 hours in an Apple store counting sales might not be the most accurate means for extrapolating data, but that’s what analysts at Piper Jaffray are using to say they think Apple is going to have its best sales quarter ever for Mac computers.

Last quarter, the company sold 2.6 million Macs, its best numbers ever. Piper Jaffray’s Gene Munster (who always seems very bullish on Apple) thinks Apple will at least match that this quarter after seeing that Apple stores are selling an average of 36 Macs per store, per day.

Munster also sees very strong iPhone sales for the quarter despite earlier reports of a big slow down in production. Right now, Apple is thought to be selling an average of 28 iPhones per day per store nationwide, which is well below the 95 a day it was selling around the iPhone 3G launch — but, worldwide sales, Best Buy sales and holiday sales could bring those two numbers closer together. (And just imagine if Apple actually does discount the phone for the holidays.)

That should mean more than 6 million iPhones sold once again for the quarter, close to last quarter’s numbers.

If these numbers hold any weight, that’s big news in a time when the U.S. and global economies are in turmoil. Apple’s computers are still seen largely as a premium brand, but despite the conventional wisdom being that people will have less money to spend on premium products, Apple apparently isn’t having much trouble moving its product.

Of course, that’s assuming that a 25-hour survey of random Apple stores provides good data.

[photo: flickr/evelien de bruyne]